An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation

 

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dc.contributor.advisor Balona, Luis en_ZA
dc.contributor.advisor Warner, Brian en_ZA
dc.contributor.author Engelbrecht, Christian Albertus en_ZA
dc.date.accessioned 2015-12-28T06:10:08Z
dc.date.available 2015-12-28T06:10:08Z
dc.date.issued 1994 en_ZA
dc.identifier.citation Engelbrecht, C. 1994. An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/15999
dc.description Bibliography: p. 243-248. en_ZA
dc.description.abstract An intensive photometric study in the Johnson B band of ten β Cephei stars in the open cluster NGC 3293 is presented. High sampling rates of the stars' light curves allow the identification of many formerly unknown pulsation frequencies in these stars, by means of Fourier periodogram analysis. All of the stars are found to be multiperiodic, with up to five frequencies identified for individual stars. Physical parameters of the stars are determined from previous photometric results in the literature. These parameters are used to make a comparison of the observed frequencies with theoretical predictions, including the effects of rotation. The results imply a preference for first and second overtone quadrupole (l=2) pulsation in these stars, while a weak relationship between stellar mass and pulsation overtone is identified. One of the stars is identified as a member of an eclipsing binary system, only the second β Cephei star to be identified as such. Physical parameters of the system are determined. The effects of rapid rotation (specifically, the distortion of the stellar profile from a perfect sphere) on alternative methods of pulsation mode identification are investigated for a model β Cephei star. Ratios between light and velocity amplitudes show extreme differences between rotationally distorted and undistorted models, but these ratios show high sensitivity to other parameters as well. Thermally broadened spectral line profiles are calculated for the same model, for modes with l = 0 to 4 and equatorial rotation velocities up to 400 km/s. Neglect of rotational distortion is shown to lead to underestimation of true equatorial rotation velocities by as much as 253. This result confirms that observed B stars are probably rotating at break-up velocities. In summary, various aspects of the behaviour of the β Cephei stars in NGC 3293 in particular, and of β Cephei stars in general, including rapid rotators, are illuminated and augmented by this study. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Astronomy en_ZA
dc.title An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Astronomy en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Engelbrecht, C. A. (1994). <i>An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Astronomy. Retrieved from http://hdl.handle.net/11427/15999 en_ZA
dc.identifier.chicagocitation Engelbrecht, Christian Albertus. <i>"An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Astronomy, 1994. http://hdl.handle.net/11427/15999 en_ZA
dc.identifier.vancouvercitation Engelbrecht CA. An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Astronomy, 1994 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/15999 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Engelbrecht, Christian Albertus AB - An intensive photometric study in the Johnson B band of ten β Cephei stars in the open cluster NGC 3293 is presented. High sampling rates of the stars' light curves allow the identification of many formerly unknown pulsation frequencies in these stars, by means of Fourier periodogram analysis. All of the stars are found to be multiperiodic, with up to five frequencies identified for individual stars. Physical parameters of the stars are determined from previous photometric results in the literature. These parameters are used to make a comparison of the observed frequencies with theoretical predictions, including the effects of rotation. The results imply a preference for first and second overtone quadrupole (l=2) pulsation in these stars, while a weak relationship between stellar mass and pulsation overtone is identified. One of the stars is identified as a member of an eclipsing binary system, only the second β Cephei star to be identified as such. Physical parameters of the system are determined. The effects of rapid rotation (specifically, the distortion of the stellar profile from a perfect sphere) on alternative methods of pulsation mode identification are investigated for a model β Cephei star. Ratios between light and velocity amplitudes show extreme differences between rotationally distorted and undistorted models, but these ratios show high sensitivity to other parameters as well. Thermally broadened spectral line profiles are calculated for the same model, for modes with l = 0 to 4 and equatorial rotation velocities up to 400 km/s. Neglect of rotational distortion is shown to lead to underestimation of true equatorial rotation velocities by as much as 253. This result confirms that observed B stars are probably rotating at break-up velocities. In summary, various aspects of the behaviour of the β Cephei stars in NGC 3293 in particular, and of β Cephei stars in general, including rapid rotators, are illuminated and augmented by this study. DA - 1994 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1994 T1 - An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation TI - An analysis of beta cephei stars in NGC 3293 and the effects of stellar rotation UR - http://hdl.handle.net/11427/15999 ER - en_ZA


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